Names:
Nina and Jessica
Title:
Power of Cars
Goal/ Lab Question:
How much work does it take for a moving truck to stop if it is going downhill?
Notes:
There is a moving truck with a mass of 25000 lbs (1139.8093 kg) going downhill. The truckdriver slams on the breaks and stops. Find the force of friction between the tires and the asvault.
Materials used:
  • car
  • ramp
  • blocks
  • logger pro
  • counter
  • calculator
  • camera
  • meter stick (for height measurements)
Procedure:
1. Set up the fan cart tracks so that they are in a downhill postion.
2.Use a fan cart with a fan to portray a real life truck.
3. Using Logger Pro, immitate the car going downhill towards the motion sensor.
4. Mocking a human slamming the brakes, use your hand to slow down the car, with a sudden impact similar to the brakes, until it stops.
Data/calculations:


Trial.JPG
Initial Potential
(mass * gravity *height)
(.256*9.8*.1651)
.41 J

Final Potential
(mass * gravity * height)
(.256*9.8*0)
0 J

Initial Kinetic
(.5*mass*velocity squared)
(.5*.256*0)
0 J

Final Kinetic
(.5*mass*velocity squared)
(.5*.256*-1.143^2)
.17 J

Total mechanic energy
change in KE + change in PE
(Final kinetic- initial kinetic) + (final potential - initial potential)=work
(.17-0) + (0-.41)= -.24 J
work=-.24J
Reflection/conclusion:
In conclusion, the amount of work done by a truck slamming on the breaks and coming to a stop going downhill was determined by creating a mock experiment. A fan cart (without the fan) was used to mock the truck, with a mass of .256 kilograms, and a track placed on top of bricks was used to mock a hill. A group members hand acted as the break, lightly touching the car inorder to imitate the motion of the car slowing down. Then using kinetic energy, potential energy, power, and momentum we determined the work done by the truck in order to stop. The initial kinetic energy was zero and the initial potential energy was .41 Joules (mass * gravity *height) (.256*9.8*.1651). The final kinetic as .17 Joules (.5*mass*velocity squared) (.5*.256*-1.143^2.) Using those values, the change in total mechanic energy, also known as work, using (change in KE+change in PE), was equal to .58 J. However in a real life situation the mass is 1139.8093 kg. This is 4452.38 times greater than the mass of the fancart. The car had very little work done, but if it were a bigger car and hill, the amount of work done will increase in a much greater quantity.

Sources:
[[http://en.wikipedia.org/wiki/Acura_TL#Fourth_generation_.28UA8-UA9.29 (Acura|http://en.wikipedia.org/wiki/Acura_TL#Fourth_generation_.28UA8-UA9.29 ]] (Acura TL mass)